1. Field of the Invention
The present invention relates to the use of coherent energy pulses, as from high power pulsed lasers, in the shock processing of solid materials, and, more particularly, to methods and for improving properties of solid materials by providing shock waves therein where the laser beam impacts the solid material on a hidden surface. The invention is especially useful for enhancing or creating desired physical properties such as hardness, strength, and fatigue strength.
2. Description of the Related Art
Known methods for shock processing of solid materials, particularly laser shock processing solid materials, typically using coherent energy as from a laser, orient the laser beam normal, i.e., perpendicular to the workpiece.
When particular constraints of processing are created, based on the shape of the material or other geometric factors such as when attempting to laser shock harden integrally bladed rotors (IBR's), blind bores, slots, or dovetail sections, the laser beam may not have a direct, line of sight access to the area to be shock processed.
Laser shock processing techniques and equipment can be found in the U.S. Pat. No. 5,131,957 to Epstein 5,131,957, along with that of U.S. Pat. Ser. No. 08/547,012 entitled LASER PEENING PROCESS AND APPARATUS, assigned to the assignee of the present invention and hereby incorporated by reference.
Known laser shock processing systems tend to form a relatively small in cross sectional area, laser beam impacting on the surface of the workpiece. This has been accomplished since to sufficiently work a surface of workpiece, sufficient laser energy must be applied over a particular area. The smaller the area with the same amount of energy leads to a greater energy per unit area application. The more energy per unit area applied, the deeper the residual compressive stresses are applied to the workpiece.
Laser shock processing of hidden surfaces would benefit particular types and areas of workpieces if such could be accomplished.
What is needed in the art is a way to modify the laser beam to consistently and uniformly work hidden areas of the workpiece.